1. Field of the Invention
The present invention relates generally to a method and apparatus for measuring noise and correspondingly the level or loudness thereof in a product, such as a motor vehicle, during use; and more particularly, to a method for objectively monitoring and measuring the noise level and comparing the noise level to a known reference value.
2. Background of the Invention
As part of ongoing quality concerns, motor vehicle manufacturers monitor and inspect their products during and after the manufacturing process. One method of tracking vehicle quality is the use of warranty coding parameters. These parameters typically include a list of vehicle systems, individual components associated with the systems and a list of descriptors; i.e., standard descriptive words used to describe any problems or remedial action taken with respect to a particular problem. Utilizing a standard set of codes, aids in evaluating vehicle quality in a consistent and uniform manner.
Operation of a motor vehicle may result in vibrations in the vehicle that can cause noise, or more specifically undesired or unwanted sounds. These sounds are often referred to as squeaks and rattles and typically result from a particular vehicle component or combination of components. The amount of noise generated by such squeaks and rattles, particularly the level or loudness thereof generated during vehicle operation, is one quality or parameter that is monitored both during and after manufacture.
Accordingly, in an attempt to reduce the occurrences of such squeaks and rattles and determine the cause thereof, trained inspectors randomly select and subjectively evaluate vehicles for squeak and rattle noise levels. These evaluations typically entail randomly selecting a vehicle from the assembly line. Placing the vehicle on a vibration inducing apparatus, such as a vehicle shaker or “four-poster” and activating the vibration inducing apparatus to induce vibration in the vehicle. While the vehicle is shaken or vibrated an operator or technician, sitting in the vehicle operator compartment, listens to noise level, specifically the loudness of any sound, including any squeaks or rattles, occurring in the vehicle operator compartment. After listening, the operator or technician makes a subjective determination to determine if the vehicle meets acceptable noise, vibration, harshness, squeak, and rattle levels.
Systems that use a microphone in a vehicle to obtain or record and analyze sound levels exist. Such systems typically determine the cause of the sound; i.e., they primarily function as a diagnostic tool used to locate the source of the excess sound. They do not objectively measure the sound level, nor do they analyze the data obtained by the relating the sound level to the cause thereof.